Electric fuse and socket



May 7, 1957 J. F. TAYLOR ELECTRIC FUSE! AND SOCKET Filed Dec. 6, 1955 AT TORNEYS United States Patent Office ELECTRIC FUSE AND SOCKET John F. Taylor, Troy, N. Y. Application December 6, 1955, Serial No. 551,386 14 Claims. (Cl. 200-119) My invention relates to plugs and sockets therefor.

At the present time, so far as I am aware, the sockets for fuse plugs are such that a plug of substantially any ampere carrying capacity may be inserted therein. As a result, fires are often caused by overloaded circuits which, for example, might normally have a 15 ampere fuse there in but in which a plug of much higher capacity has been inserted in the socket connected in said circuit.

The fuse socket which is connected in series with each electric circuit in a building is installed by the electrical contractor who is doing the wiring and, initially, each circuit is equipped with a fuse plug of the proper capacity for the associated circuit. However, when one of these fuses blows, the householder or some other individual frequently replaces the blown fuse with a fuse of much higher capacity than is proper for the circuit.

The principal objects of my invention are to provide a socket of such design that only a fuse plug of the proper ampere carrying capacity for the circuit in which the socket is installed will function when placed in said socket; and also to provide a fuse plug having fuse elements therein of various capacities of which only the one for which the socket is designed will function when inserted therein. In other words, the plugs are all alike so that the householder need exercise no care either in purchasing or using them to see that they are of the proper capacity.

A further object is to provide a simple element which may be readily inserted in a socket of the ordinary present type whereby the socket is converted into one adapted to cooperate with one of my plugs of the proper capacity for the circuit in which the socket is connected.

I accomplish these objects by the means described below and illustrated in the accompanying drawing in which- Fig. 1 is a vertical section of my socket showing it as it would be installed in a circuit requiring a 30 ampere fuse;

Fig. 2 is a top view of my fuse plug;

Fig. 3 is a vertical section through said plug; and

Fig. 4 is an elevation view of a screw which is substituted for the screw shown in the center of Fig. 1 when the circuit in which the socket is placed requires a 5 or ampere fuse.

Referring to the drawing, and first to Figs. 2 and 3, my plug is indicated generally by the numeral 1, and, insofar as the size and shape are concerned, it does not difier very much from fuse plugs of the present type. The top portion 2 is formed of transparent glass so that the condition of the fuses therein may be readily observed. 3 is an element formed of insulating material, such as plastic, the lower portion of which is preferably, but not necessarily, frusto-conical. The upper portion is cylindrical, adapted to fit within the glass portion 2, and is provided intermediate said portions with an annular shoulder 4 which serves to secure it in the glass portion of the fuse by means of the externally threaded sheet metal improvements in electric i use 2,791,661 Patented May 7, 1957 conductor 5 which is adapted to cooperate with an internally threaded conductor in the socket for securing the plug therein. The bottom of the conductor 5 is inturned, as shown at 6, to secure the parts of the plug together.

Molded within the plastic 3 is a center conductor 7 having at the bottom an exposed contact 8. Also molded in the plastic is a second conductor 9 terminating at the lower end in an exposed portion 10 which is to be understood as extending partially around the surface of the portion 3; and a third conductor 11 which terminates at the bottom in an exposed portion 12 axially spaced from the exposed portion 10 and which is also understood to extend partially around the portion 3.

13 is a fuse element having 3 laterally spaced portions 14, 15 and 16 of different ampere carrying capacity, for example, 5, 10 and 15 amperes. The fuse element 13 is electrically connected to the threaded metal shell 5 at 17, and the spaced portions 14, 15 and 16 are electrically connected to the tops of the conductors 9, 11 and 7, respectively.

Referring now to Fig. 1, the socket comprises a base 18 formed of porcelain or the like, and which is provided with terminals 19 and 20 for connecting the socket in an electrical circuit. Mounted on the base 1 is an internally threaded metal conductor shell 21 adapted to receive the threaded portion 5 of the plug in order to secure it in said socket. This shell is electrically connected to the terminal 19 at 22 by soldering or otherwise.

Within the shell at the bottom thereof is a block 23 of insulating material, preferably plastic, having therein a recess 24 which is substantially complementary in shape to the portion 3 of the plug 1. In other words, when the plug is screwed into the socket the complementary surfaces of the plug and socket will come into contact with each other.

As illustrated in Fig. l, a conductor 25 having portions 26 and 27 exposed in the surface of the recess is molded in the block 23. The exposed portions are axially spaced so that when the plug is screwed into the socket they will be in contact with the exposed portions 10 and 12, respectively, of the conductors in the plug. As illustrated, the block 23 is secured to the base by means of the screw 28, the top of which will be electrically connected to the contact 8 at the bottom of the plug when the plug is in the socket. The screw 28 is also in electrical contact with the conductor 25 and is electrically connected to the terminal 20 by means of the element 29.

While the plugs 1 used in my device are all identical, the sockets would be modified in accordance with the proper fuse capacity of the circuit in which they are installed. As illustrated, all three of the spaced portions of the fuse would be capable of carrying current when the plug is installed in the socket and therefore the ampere carrying capacity thereof, if the spaced portions of the fuse had capacities of 5, 10 and 15 amperes, would be 30 amperes.

If a 25 ampere capacity were desired, that portion of the conductor 25 in the socket which is exposed at 2-6 would be omitted so that the current carrying capacity of the fuse would be limited to the portions 15 and 16.

Similarly, if a 20 ampere capacity were proper for the circuit in which the socket is installed, that portion of the conductor 25 which is exposed at 27 would be omitted so that the current carrying capacity of the fuse would be limited to the portions 14 and 16 thereof.

If a 15 ampere fuse were proper, either the conductor 25 would be omitted, or a screw such as shown at 30 in Fig. 4 would replace the screw 28. The screw 3t) would have an insulator 31 applied to the top thereof by cementing or otherwise securing it thereto so that when the plug is screwed in the socket the portion 16 of the fuse would not form a part of the conductor through the plug because the contact 8 at the bottom of the plug would not contact the screw 30. The portions 26 and 27 of the conductor 25 in the socket would remain asshown in Fig. 1 so that the current carrying capacity of the plug would be limited to the portions 14 and 15 of the fuse element. On the other hand, if the conductor 25 were omitted without changing the screw 28, the fuse portion 16 would function alone.

If a 10 ampere capacity were proper for the circuit, the screwGii would replace the screw 28 and the exposed portion 26 of the conductor 25 would be omitted so that current could only flow through the portion 15 of the fuse element. Similarly, if a ampere capacity were proper for the circuit, the screw 30 would replace the screw 23 and the exposed portion 27 of the conductor 25 would be omitted so that current could only flow through the portion 14 of the fuse element.

While I have mentioned the relative current carrying capacities of the spaced portions of the fuse element as 5, and amperes, it is to be understood that the current carrying capacities of these portions may be varied as desired.

From the foregoing it will be apparent that where the electrician who installs the wiring places the proper current carrying capacity socket in the circuit, a plug having any greater or less current carrying capacity than that which is proper for the circuit would be inoperative if placed in the socket. In addition to this advantage, the householder would not have to ascertain the current carrying capacity of the plug to be inserted in any socket because the plugs would be all alike and would function properly in any of the sockets.

An ordinary socket of the type now universally used may be readily converted into a socket adapted to cooperate With my plug by merely inserting therein a block like that shown at 23 and securing it by means of a screw (29 or 30) of the proper type to fix the current carrying capacity of the plug when inserted in the socket.

While I have described my invention in its preferred embodiment, it is to be understood that the words which I have used are words of description rather than limitation and that changes, within the purview of the appended claims, may be made without departing from the true scope and spirit of my invention in its broader aspects.

What I claim is:

1. An electric fuse plug comprising an externally threaded conductor adapted to cooperate with a threaded socket for securing said plug therein; a fuse element within said plug comprising at least two spaced portions of different current-carrying capacity electrically connected to said conductor; a portion of said plug formed of insulating material depending below said threaded conductor having a first conductor therein electrically connected to one of the portions of said fuse element and terminating in an exposed contact at the bottom of said depending portion; and a second conductor in said depending portion electrically connected to another portion of said fuse element of different current-carrying capacity and terminating in a portion exposed on the surface of said depending portion.

2. The structure set forth in claim 1 in which said depending portion has an inverted frusto-conical lateral surface.

3. An electric fuse plug comprising an externally threaded conductor adapted to cooperate with a threaded socket for securing said plug therein; a fuse element within said plug comprising a plurality of spaced portions of different current-carrying capacity electrically connected to said conductor; a portion of said plug formed of insulating material depending below said threaded conductor and having a first conductor therein connected to one portion of said fuse element and terminating in an exposed contact at the bottom of said depending portion; and other conductors in said depending portion each electrically connected to a different portion of said fuse element, and terminating in portions exposed on the surface of said depending portion in axially spaced Zones thereof.

4. The structure set forth in claim 3 in which said depending portion has an inverted frusto-conical lateral surface.

5. The structure set forth in claim 3 in which there are three separate conductors in said depending portion; and said spaced portions of said fuse element having current-carrying capacities of 5, l0 and 15 amperes, respectively.

6. A socket for a fuse plug comprising a base having two terminals thereon for connecting said socket in an electric circuit; an internally threaded conductor adapted to cooperate with an externally threaded conductor on said plug for securing said plug in said socket; means electrically connecting said internally threaded conductor to one of said terminals; a block of insulating material having a recess therein coaxial with said threaded conductor and adapted to contact a substantially complementary portion of said fuse plug when said plug is secured in said socket; said block having a conductor therein with at least one portion thereof exposed in the lateral surface of said recess intermediate the top and bottom thereof; and means electrically connecting the conductor in said block to the other of said terminals.

7. The structure set forth in claim 6 in which said recess has an inverted frusto-conical sulface.

8. A socket for a fuse plug comprising a base having two terminals thereon for connecting said socket in an electric circuit; an internally threaded conductor adapted to cooperate with an externally threaded conductor on said plug for securing said plug in said socket; means electrically connecting said internally threaded conductor to one of said terminals; a block of insulating mate rial having a recess therein coaxial with said threaded conductor and adapted to contact a substantially complementary portion of said fuse plug when said plug is secured in said socket; said block having a conductor therein with a plurality of portions thereof exposed in the surface of said recess in axially spaced zones thereof; and means electrically connecting the conductor in said block to the other of said terminals.

9. The structure set forth in claim 8 in which said recess has an inverted frusto-conical surface.

10. The combination with an electric fuse plug comprising an externally threaded conductor portion; a fuse element within said plug comprising spaced portions of different current-carrying capacity electrically connected to said threaded conductor; an inverted frusto-conical portion formed of insulatiing material and having conductors exposed in axially spaced zones of the surface thereof each electrically connected to said fuse element but through said portions thereof having different current-carrying capacities; and a socket for said plug comprising a base having two terminals thereon for connecting said socket in an electric circuit; an internally threaded conductor electrically connected to one of said terminals cooperating with the threaded conductor on said plug for securing said plug in said socket; and insulating means in said socket having a recess therein complementary to the frusto-conical portion of said plug and having at least one conductor exposed on the surface of said recess electrically connected to the other of said terminals and adapted to contact with one of the exposed conductors on the frusto-conical portion of said plug when said plug is secured in said socket.

11. An adapter for converting a fuse plug socket of the type in which plugs of various current-carrying capacity will function when inserted, into a socket in which only a plug of a predetermined current-carrying capacity will function when inserted therein; said adapter comprising a block of insulating material of a size adapted to be inserted and secured in the lower portion of said socket by means of a screw extending through the bottom thereof; said block having a centrally disposed recess therein, open at the top, and adapted to receive a portion of said plug of predetermined capacity in contact with the sidewall thereof; and a conductor in said block having a portion thereof which will be in electrical contact with said screw when said block is secured in said socket, and at least one other portion exposed in the side wall of said recess.

12. The structure set forth in claim 11 in which the side wall of said recess has an inverted frusto-conical surface.

13. An adapter for converting a fuse plug socket of the type in which plugs of various current-carrying capacity will function when inserted, into a socket in which only a plug of a predetermined current-carrying capacity will function when inserted therein; said adapter comprising a block of insulating material of a size adapted to be inserted and secured in the lower portion of said socket by means of a screw extending through the bottom thereof; said block having a centrally disposed recess therein, open at the top, and adapted to receive a portion of said plug of predetermined capacity in contact with the side wall thereof; and a conductor in said block having a portion thereof which will be in electrical contact with said screw when said block is secured in said socket, and other portions exposed in the side wall of said recess in vertically spaced zones thereof.

14. The structure set forth in claim 13 in which the side wall of said recess has an inverted frusto-conical surface.

References Cited in the file of this patent UNITED STATES PATENTS 1,682,365 Bourgeois Aug. 28, 1928 

